Plate Heat Exchanger

ABSTRACT

A plate heat exchanger has openings in the plates defining supply and return ducts extending through a plate stack. The supply and return ducts are hydraulically connected to flow ducts located between the plates and to a tube arranged coaxially in each of the supply and return duct. The tubes have holes in the tube wall in order to provide the hydraulic connection to the flow ducts. A simple and cost-effective plate heat exchanger which can withstand high pressures is achieved by the tubes extending through the entire stack to form a tie rod between a top side and an underside of the plate stack. The tube has a diameter corresponding to the diameter of the openings in the plates such that the tube wall is firmly metallurgically connected to at least some edges of the openings.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Patent Application No. 102015 010 289.3 filed Aug. 20, 2015, the entire contents of which arehereby incorporated by reference herein.

FIELD OF THE INVENTION

The invention relates to a plate heat exchanger having openings in theplates, which are formed by supply or return ducts extending through aplate stack, said supply or return ducts being hydraulically connectedto flow ducts located between the plates. and to a tube arrangedcoaxially in the supply or return duct, having holes in the tube wall ofsaid tube for providing the hydraulic connection to the flow ducts.

BACKGROUND

U.S. Pat. No. 3,976,128A discloses an evaporator which is constructed asa plate and fin heat exchanger. In order to improve the performancethereof, the tube was arranged in the supply duct coaxially with theholes in the tube wall of said tube. The performance improvement isachieved by specific positioning, proposed therein, of the holes at thecircumference of the tube wall. The strength of the known heat exchangercannot be improved to the extent that would be desired and alsonecessary at particularly high internal pressures.

In the case of a known plate heat exchanger used as an oil cooler (shownas the prior art heat exchanger of FIG. 12) solid annular discs R arearranged between the plates in the region of the opening edges in orderto control the high internal pressure

SUMMARY

One problem addressed by the invention is to simplify the production ofthe plate heat exchanger, without neglecting the strength thereof.

According to one aspect of the invention, the tube extends through theentire stack in order to form a tie rod between a top side and anunderside of the plate stack. The tube has a diameter corresponding tothe diameter of the openings in the plates such that the tube wall isfirmly connected metallurgically to at least some edges of the openings.In order to reinforce the abovementioned metallic connection, at leastsome of the opening edges are provided with a flange bearing against thetube wall.

The abovementioned terms “top side” and “underside” are primarilyindependent of their spatial arrangement, i.e. should be understood astwo opposite sides of the plate stack.

As a consequence of the implementation of the invention, the previouslyprovided solid annular discs can be dispensed with. On account of thecoaxial tube being configured as a tie rod, the plate heat exchangeraccording to the invention has sufficient strength with respect to veryhigh internal pressures. It is lighter than the previous heat exchangersand it has also become producible with lower costs on account of thenumerous annular discs being dispensed with.

The provision of flanges or collars at the opening edges simultaneouslyalso serves for the firm metallic connection between adjacent openingedges of adjacent plates, with the result that the hydraulic separationbetween the flow ducts is achieved.

The proposed solution can be applied in plate heat exchangers which arearranged in a housing and also in what are known as “housingless” plateheat exchangers, as is otherwise also apparent from the followingdescription of exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of a plate heat exchanger according toan embodiment of the invention, which is to be arranged in a housing(not shown).

FIG. 2 shows a longitudinal section through this plate heat exchanger.

FIG. 3 is an enlarged illustration of a tube which is located coaxiallyin the supply duct and in the return duct of the plate heat exchanger.

FIGS. 4A-4C contain several illustrations of differently designed tubes.

FIG. 5 is similar to FIG. 1, but omits key features from FIG. 1 andinstead shows details which are not visible in FIG. 1.

FIG. 6 is an enlarged detail view of the area indicated as IV in FIG. 3.

FIGS. 7-10 show enlarged details of different opening edges which aremetallurgically connected to the coaxial tube, to be more precise withthe tube wall thereof.

FIG. 11 shows a plan view of a “housingless” plate heat exchanger as anoutline with in each case one coaxial tube in the supply and returnducts thereof.

FIG. 12 shows a longitudinal section of a plate heat exchanger from theprior art, which has solid rings R introduced between the plates aroundthe hole edges.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the accompanyingdrawings. The invention is capable of other embodiments and of beingpracticed or of being carried out in various ways. Also, it is to beunderstood that the phraseology and terminology used herein is for thepurpose of description and should not be regarded as limiting. The useof “including,” “comprising,” or “having” and variations thereof hereinis meant to encompass the items listed thereafter and equivalentsthereof as well as additional items. Unless specified or limitedotherwise, the terms “mounted,” “connected,” “supported,” and “coupled”and variations thereof are used broadly and encompass both direct andindirect mountings, connections, supports, and couplings. Further,“connected” and “coupled” are not restricted to physical or mechanicalconnections or couplings.

The exemplary embodiments described in the following text make itpossible to dispense with the abovementioned rings R, but to retain highinternal-pressure resistance of the plate heat exchanger.

The plate heat exchanger in the exemplary embodiments shown is an oilcooler for cooling oil, for example transmission oil, by means of acoolant, without being limited thereto.

The plate heat exchanger according to FIGS. 1-3 and 5-10 has twoopenings 1 in all of the plates 2. The plates 2 have been stacked toform a plate stack 3 such that, by means of the openings 1, supply ductsand a return ducts extending through the plate stack 3 are formed, whichboth have the reference sign 10. The two ducts 10 are hydraulicallyconnected to flow ducts 11 located between the plates 2. As FIG. 2shows, oil flows into the supply ducts 10 (on the right), flows throughthe flow ducts 11 and, after corresponding cooling, passes into thereturn duct 10 (on the left). A further flow duct 11.1 is in each caselocated between the flow ducts 11. The flow ducts 11.1 are flowedthrough by the coolant. The coolant is symbolized by block arrowsarranged on the left and right (FIG. 2). The housing (not shown) hascorresponding openings (not shown) for the entry and exit of the liquidcoolant.

Fins (not illustrated) or the like are optionally provided in the flowducts 11. Studs 13 that butt against one another or similar plateformations are provided in the flow ducts 11.1 of the exemplaryembodiment. The studs 11 can be replaced, for example also by otherfins.

A coaxially arranged tube 4 is located in both the supply duct and thereturn duct 10. The tube 4 has holes 40 arranged in the tube wall 41thereof. The holes 40 allow the mentioned hydraulic connection to theflow ducts 11 and have therefore been arranged exactly at the heights ofthe flow ducts 11. The shape of the holes 40 can vary. FIG. 2 showsround holes 40. FIGS. 3 and 4 show elongate holes 40. Further shapes andalso different cross-sectional sizes are conceivable and have also beencontemplated for other embodiments of the invention that are not shown.

With regard to the through-flow of the flow ducts 11, the arrangement,discernible in FIG. 5, of the holes 40 has proved advantageous. It canbe seen therein that the tube wall 41 is formed in a circumferentialportion 44, directed in the longitudinal direction of the plate heatexchanger, without holes 40. As a result, all regions of the flow ducts11 are flowed through better, that is to say are involved better in heatexchange, this being advantageous with regard to efficiency. Aconsiderable quantity of oil is initially forced to flow around thesupply duct 10 before it flows in the longitudinal direction, or in thedirection of the return duct 10. The return duct 10 is also initiallyflowed around before the oil passes into same.

The tube 4 has a tie-rod function. Therefore, it extends through theentire stack 3 and is firmly metallurgically bonded to a top side and anunderside of the plate stack 3. In the embodiment of FIGS. 1-3,thick-walled flanges 9 are provided on the top side, which rest on amore stable plate 8. The stack 3 also has a stable lower plate 7 on theunderside. As is best discernible from FIGS. 3 and 6, a brazing gap 43has been provided to enhance the tie-rod functionality, said brazing gap43 contributing considerably to the strength of the brazed connectionbecause it will receive a larger quantity of braze material. A ring 45of braze alloy may be necessary if the provided amount of braze isinsufficient. Furthermore, a collar 80 on the upper plate 8 cancontribute to increasing the strength. The collar 80 can project intothe gap 43. A similar collar can be located at a corresponding hole inthe lower plate 7.

A further contribution with regard to the strength is achieved in thatthe tube 4 has a diameter corresponding to the diameter of the openings1 in the plates 2. In this way, the tube wall 41 is firmly connectedmetallurgically, preferably brazed, to all of the edges 6 of theopenings 1 in the exemplary embodiment. At least some opening edges 6should have the connection.

FIGS. 7-10 show partial cross-sectional views of various possiblealternative design details for select embodiments of the invention.Certain less relevant details of the plate heat exchanger have beenremoved or simplified in order to best illustrate the details ofinterest. Each of FIGS. 7-10 show only half an opening edge, or half atube 4, this being made clear by the indicated axis A. In addition, thenumber of flow ducts illustrated has been reduced to a single open flowduct arranged between two closed flow ducts. While most embodiments ofthe invention will include more of each kind of flow duct, suchadditional flow ducts can be provided by repeating instances of thedepicted geometry, and thus do not need to be shown in order toadequately describe the invention. Additionally, those portions of theheat exchanger along the longitudinal direction between the end of thethick-walled flange and the far ends of the plates have been removed forthe figures, but are as shown in FIG. 2.

It is highly advantageous for the edges 6 to be provided with a flangeor collar 60 bearing against the tube wall 41 (FIG. 7), in order tofurther strengthen the metallic connection. As shown in FIGS. 7-10, sucha flange 60 is provided on alternating ones of the plates 2. Theadjacent and interleaved ones of the plates 2 are provided with anopening 1 that is larger in diameter than the opening 1 provided inthose plates having a flange 60. In this manner, the flanges 60 can bemetallurgically joined to the tube 4 to provide structural strengthalong the stack height, while other metallurgical joints between theadjacent plates are provided immediately adjacent to and radiallyoutward of the supply and return ducts 40 in order to hydraulicallyseparate the closed flow ducts for the oil from the open flow ducts forthe liquid coolant.

The interleaved plates 2 that are not directly bonded to the tube 4 canstill be provided with a flange along the opening edge, as shown in thealternative of FIGS. 9 and 10. Adjacent plates 2 can be joine to oneanother at the flanges as shown, so that the aforementioned flange 60 isarranged between the tube wall 4 and the flange of the adjacent plateand is bonded to both, thereby further increasing the strength of thetie-rod. In order to increase the rigidity of the edges 6, it is alsopossible to additionally form a circumferential protuberance 14, asshown in FIG. 10.

At an end located opposite an inlet 30 or an outlet 50, the coaxial tube4 has a closure cap 42 or the like firmly connected metallurgically tothe tube 4. The closure cap 42 can be a differently formed individualpart (FIGS. 4A and 4B). It can also be formed in one piece with the tube4, however, as is shown in the design according to FIG. 4C.

The outline according to FIG. 11 is intended merely to show that theproposed subject matter can also be implemented in what is known as a“housingless” plate heat exchanger of known construction.

As is known, this differs from the above in that the plate stack 3 hassecond flow ducts 12 (not shown, merely indicated by means of an arrow)located between the plates 2, said second flow ducts 12 beinghydraulically connected to second supply or return ducts 20 formed fromsecond plate openings 5, wherein the tube 4 is also or only located inone of the second supply or return ducts 20, wherein the holes 40 in thetube wall 41 of said tube provide the hydraulic connection to the secondflow ducts 12. Dashed circles are intended to indicate inserted tubes 4in all supply and return ducts 10, 20.

Various alternatives to the certain features and elements of the presentinvention are described with reference to specific embodiments of thepresent invention. With the exception of features, elements, and mannersof operation that are mutually exclusive of or are inconsistent witheach embodiment described above, it should be noted that the alternativefeatures, elements, and manners of operation described with reference toone particular embodiment are applicable to the other embodiments. Theembodiments described above and illustrated in the drawings arepresented by way of example only and are not intended as a limitationupon the concepts and principles of the present invention. As such, itwill be appreciated by one having ordinary skill in the art that variouschanges in the elements and their configuration and arrangement arepossible without departing from the spirit and scope of the presentinvention.

What is claimed is:
 1. A plate heat exchanger comprising: a plurality ofplates arranged to form a plate stack, first openings of the platesaligned to form a supply duct extending through the plate stack andsecond openings of the plates aligned to form a return duct extendingthrough the plate stack, flow ducts being located between the plates tohydraulically connect the supply and return ducts; a first tube arrangedwithin the supply duct and extending through the entire plate stack, afirst end of the first tube being metallurgically joined to a top sideof the plate stack and a second end of the first tube beingmetallurgically joined to a bottom side of the plate stack in order tofunction as a first tie-rod connection through the plate stack; and asecond tube arranged within the return duct and extending through theentire plate stack, a first end of the second tube being metallurgicallyjoined to a top side of the plate stack and a second end of the secondtube being metallurgically joined to a bottom side of the plate stack inorder to function as a second tie-rod connection through the platestack.
 2. The plate heat exchanger of claim 1, further comprising: afirst thick-walled flange arranged at the top side of the plate stackand joined to an uppermost plate of the plate stack, the inlet ductextending through the first thick-walled flange, wherein themetallurgical joint at the first end of the first tube is located withinthe first thick-walled flange; and a second thick-walled flange arrangedat the top side of the plate stack and joined to the uppermost plate ofthe plate stack, the return duct extending through the secondthick-walled flange, wherein the metallurgical joint at the first end ofthe second tube is located within the second thick-walled flange.
 3. Theplate heat exchanger of claim 2, wherein the metallurgical joints a thefirst end of the first and second tubes comprise braze material arrangedin one or more gaps between the first end of the first and second tubesand the first and second thick-walled flanges, respectively.
 4. Theplate heat exchanger of claim 1, wherein the first and second tubes eachcomprise a closure cap metallurgically connected to the second end ofsaid tube.
 5. The plate heat exchanger of claim 1, wherein: at leastsome of the first openings are provided with first flanges defining adiameter of said first openings that corresponds with a diameter of thefirst tube, the first tube being metallurgically joined to the firstflanges; and at least some of the second openings are provided withsecond flanges defining a diameter of said second openings thatcorresponds with a diameter of the second tube, the second tube beingmetallurgically joined to the second flanges.
 6. The plate heatexchanger of claim 5, wherein: the first tube includes a plurality offirst holes arranged in a wall of the first tube, the plurality of firstholes being arranged between those locations where the first tube ismetallurgically joined to the first flanges in order to provide ahydraulic connection between the supply duct and the flow ducts; and thesecond tube includes a plurality of second holes arranged in a wall ofthe second tube, the plurality of second holes being arranged betweenthose locations where the second tube is metallurgically joined to thesecond flanges in order to provide a hydraulic connection between thereturn duct and the flow ducts.
 7. The plate heat exchanger of claim 6,wherein the first and second tubes each include a circumferential wallportion, directed in a longitudinal direction of the plate heatexchanger, that is without any of the first and second holes.
 8. Theplate heat exchanger of claim 6, wherein the pluralities of first andsecond holes are arranged so that a considerable quantity of fluidreceived into the supply duct is initially forced to flow around thesupply duct before flowing in a longitudinal direction of the plate heatexchanger and a considerable quantity of fluid received from the flowducts is initially forced to flow around the return duct before beingreceived into the return duct.
 9. The plate heat exchanger of claim 5,wherein at least some of the first openings are of a diameter that islarger than the diameter of the first tube and wherein at least some ofthe second openings are of a diameter that is larger than the diameterof the second tube.
 10. The plate heat exchanger of claim 9, wherein theflow ducts are hydraulically isolated from cooling fluid flow ductsarranged between the flow ducts by metallurgical joints between plateshaving a first flange and plates having a first opening of a diameterthat is larger than the diameter of the first tube, and by metallurgicaljoints between plates having a second flange and plates having a secondopening of a diameter that is larger than the diameter of the secondtube.
 11. The plate heat exchanger of claim 10, wherein those firstopenings having a diameter that is larger than the diameter of the firsttube are provided with third flanges, at least some of those thirdflanges being metallurgically bonded to the first flanges.
 12. The plateheat exchanger of claim 10, wherein those second openings having adiameter that is larger than the diameter of the second tube areprovided with third flanges, at least some of those third flanges beingmetallurgically bonded to the second flanges.
 13. A plate heat exchangercomprising: a plurality of plates arranged to form a plate stack,adjacent plates in the plate stack being spaced apart to provide a firstplurality of closed flow ducts for a flow of oil through the plate heatexchanger and a second plurality of open flow ducts for a flow of liquidcoolant through the plate heat exchanger, the first and secondpluralities of flow ducts being arranged in alternating sequence; afirst tube extending through the entire plate stack to provide a supplyduct for the flow of oil, the first tube having a plurality of holes tohydraulically connect the first plurality of flow ducts to the supplyduct; and a second tube extending through the entire plate stack toprovide a return duct for the flow of oil, the second tube having aplurality of holes to hydraulically connect the first plurality of flowducts to the return duct, wherein at least some of the plurality ofplates are metallurgically joined to the first tube and the second tube.14. The plate heat exchanger of claim 13, wherein the pluralities ofholes in the first and second tubes are arranged in intervals along astacking direction of the plate stack, the metallurgical joints betweensaid at least some of the plurality of plates and the first and secondtubes being located between the intervals.
 15. The plate heat exchangerof claim 14, wherein the first and second tubes each include acircumferential wall portion, directed in a longitudinal direction ofthe plate heat exchanger, that is without any of the holes.
 16. Theplate heat exchanger of claim 14, wherein the pluralities of holes arearranged so that a considerable quantity of oil received into the supplyduct is initially forced to flow around the supply duct before flowingin a longitudinal direction of the plate heat exchanger and aconsiderable quantity of oil received from the closed flow ducts isinitially forced to flow around the return duct before being receivedinto the return duct.
 17. The plate heat exchanger of claim 13, whereineach of the plates includes a first opening coaxially aligned with thefirst tube and a second opening coaxially aligned with the second tube,at least some of the plurality of plates being provided with a flangealong a continuous edge of the first opening, at least some of theplurality of plates being provided with a flange along a continuous edgeof the second opening, the metallurgical joints between the plates andthe first and second tubes being provided at the flanges.
 18. The plateheat exchanger of claim 17, wherein the plurality of plates comprises: aplurality of first plates, each of which is provided with a flange alonga continuous edge of at least one of the first and second opening, saidflange being metallurgically joined to the corresponding one of thefirst and second tubes; and a plurality of second plates interleavedwith the first plates, each of the second plates being metallurgicallyjoined to an adjacent one of the plurality of first plates at a firstlocation adjacent to and radially outward of the first tube and at asecond location adjacent to and radially outward of the second tube inorder to hydraulically separate the first plurality of closed flow ductsfrom the second plurality of open flow ducts.
 19. The plate heatexchanger of claim 18, wherein at least some of said metallurgicaljoints between the first plates and the second plates are located atsaid flanges.
 20. The plate heat exchanger of claim 13, furthercomprising: a first thick-walled flange arranged at a top side of theplate stack and joined to an uppermost plate of the plate stack, theinlet duct extending through the first thick-walled flange, an end ofthe first tube being metallurgically joined to the first thick-walledflange; and a second thick-walled flange arranged at the top side of theplate stack and joined to the uppermost plate of the plate stack, thereturn duct extending through the second thick-walled flange, an end ofthe second tube being metallurgically joined to the second thick-walledflange.